Fluid heater appliance

ABSTRACT

A fluid heating appliance of the stackless type particularly adapted for heating swimming pool water. A rectangular housing or cabinet is assembled and contains a combustion chamber, a heat exchanger capable of carrying the fluid to be heated and disposed within said combustion chamber whereby to intercept the flow of combustion products, a flue collector immediately adjacent said heat exchanger, a flue products outlet chamber or duct adjacent said flue collector and adapted to receive the combustion products from the flue collector and having an outlet for discharge of collected combustion products to the atmosphere, a fresh-air intake, a control chamber communicating between said fresh-air intake and said combustion chamber, a restricted aperture disposed between said fresh-air intake and said control chamber for aspirating a given quantity of air to the control chamber and at least one passageway communicating between said fresh-air intake and the exterior of the appliance by-passing said control chamber whereby in adverse weather conditions, any excessive quantity of air is directed by way of said passageway for discharge to the atmosphere by-passing said control chamber, yet without requiring the use of additional draft diverters, baffles, spoilers and the like structures.

United StatesPatent n 1 Schindler et al.

ill] 3,800,748 [451 I Apr. 2, 1974 FLUID HEATER APPLIANCE [75] Inventors: Herbert Schindler, North Hollywood; Willard 0. Ware, Stockton, both of Calif.

73 Assignee: M.M.S. Limited, Alameda, Calif.

22 Filed: Jan. 8, 1973 21 Appl.No.:322,074

[52] US. Cl. 122/367 C, 126/85 B, 126/307 A Primary Examiner-Kenneth W. Sprague Assistant Examiner-James C. Yeung Attorney, Agent, or Firm-Silverman & Cass [57] ABSTRACT v A fluid heating appliance of the stackless type particularly adapted for heating swimming pool water. A rectangular housing or cabinet is assembled and contains a combustion chamber, a heat exchanger capable of carrying the fluid to be heated and disposed within said combustion chamber whereby to intercept the flow of combustion products, a flue collector immediately adjacent said heat exchanger, a flue products outlet chamber or duct adjacent said flue collector and adapted to receive the combustion products from the flue collector and having an outlet for discharge of collected combustion products to the atmosphere, a fresh-air intake, a control chamber communicating between said fresh-air intake and said combustion chamber, a restricted aperture disposed between said freshair intake and said control chamber for aspirating a given quantity of air to the control chamber and at least one passageway communicating between said fresh-air intake and the exterior of the appliance bypassing said control chamber whereby in adverse weather conditions, any excessive quantity of air is directed by way of said passageway for discharge to the atmosphere by-passing said control chamber, yet without requiring the use of additional draft diverters, baffles, spoilers and the like structures.

" 34 Claims, 13 Drawing Figures "ATENTEU PR 2 l3 FIG. 4

PAIENTEOAPR 2mm 3800 748 SHEET 3 BF' 3 FLUID HEATER APPLIANCE FIELD OF THE INVENTION This invention relates generally to fluid heaters and more particularly is directed to a fluid heater of the stackless type for heating swimming pool water, said heater having air aspirating means capable of directing sufficient air into the combustion chamber thereof while discharging excessive air and the flue products of combustion whereby to render the operation of the appliance independent of varying wind velocities.

BACKGROUND OF THE INVENTION Generally, fluid heater appliances particularly of the type which are intended for outdoor use which are adapted for heating swimming pool water for example, are of the gas burning type in preference to other fuel use. Such gasburning appliances usually are provided with a combustion chamber having a gas burner located therein. In such devices, a quantity of gas and air under pressure is supplied to the burner in such a manner that the air-gas mixture is ignited by a pilotburner as it leaves the burner unit through burner ports. Thereafter, the gas and air mixture continuously combusts within the combustion chamber. A quantity of socalled secondary air, that is, fresh air, also enters into the combustion chamber from an intake opening so as to mix with the original gas-air mixture there to complete the combustion process.

Accordingly, complete combustion of the gas is accomplished within the combustion chamber. The socalled flue products of combustion rise within the combustion chamber and are exhausted through a port or outlet located above said combustion chamber. Heat transfer devices are located below the port or outlet directly in the path of the combustion products. Generally, the heat transfer device is a heat exchanger including a plurality of conduits extending to intercept the flue product flow whereby the generated heat energy is transferred through the device to heat a fluid traveling through the conduits. Thereafter the flue products are vented through the port or outlet to the atmosphere. Additionally, the combustion per se generates radiant heat also partially absorbed by the heat exchanger and transferred to the fluid passing therethrough. The pressure relationships within the heater are such that the hot products of combustion rise within the combustion chamber and exit through the outlet or port because of the difference in static pressure that results from the reduced weight of the column of flue products of combustion in their heated state as compared to their state at ambient temperature. The aforesaid static pressure differential is called draft and more specifically is described as natural draft.

Normally, gas burning appliances have been provided with various means for equalizing the static air pressure at the outlet with the static air pressure existing at the fresh air intake. This fresh air is referred to in the art as so-called secondary air in contrast to the primary air forming the air-gas combustible mixture. Imbalance in the static air pressures adversely effects the combustion characteristics within a reasonable range of draft. Most known gas-burning appliances of this type normally permit completion of the combustion within the combustion chamber. However, excessive draft sometimes referred to as updraft or downdraft depending upon the location of the imbalance, usually causes either incomplete combustion, poor flame stability, flashing of the flame or combustion outside the combustion chamber, extinction of the flames, poor heat exchange or similar conditions which are not only undesirable but may be hazardous and dangerous. If the static air pressure were greater at the outlet port, a so-called downdraft would be created which would enter the combustion chamber through the outlet port and cause the burner flame to deflect or mushroom sometimes passing outside the combustion chamber. This would probably result in substantial damage to the temperature controls, usually thermostatically operated. Conversely, if the static air pressure were greater at the intake, then an updraft would be created and an excessive amount of combustion air would pass through the chamber causing the burner to lift and carry a significant amount of the generated heat out of the chamber without permitting or performing any useful work. Many devices of this character locate their air intake near the bottom of the appliance close to the gas burners and remote from the outlet port. The distance itself makes possible a substantial difference in static air conditions between the inlet or intake and the outlet.

However, excessive drafts which may be created by adverse wind conditions such as gusts, storms, act directly on the appliance or at least act indirectly by reflection from nearby structures. Such drafts further add to the imbalance causing draft conditions which are detrimental to the efficient operation of the appliance. There is a safety factor in directing a significant amount of uncombusted products to the atmosphere by way of the outlet and of course, often causes extinguishment of the pilot burner. This results in down-time and erratic operation.

Heretofore, prior gas burning appliances of this type included a stack connected to the outlet to permit the outlet to function independently of wind velocities and static air pressure around or near the stack. However, notwithstanding the provision of simple stacks, downdrafts still occur. Accordingly, various means such as draft diverters, barometric dampers, vent hoods or covers, spoilers or the like are required to correct deficiencies described. A draft diverter provides a relief opening through which any downdrafts from the atmosphere are spilled or deflected into a surrounding area rather than entering the flue ways of the appliance itself. A barometric damper is an adjustable device of the same type and function. A vent hood is a device that is usually located at the terminal point of the stack to deflect the downdraft and further to protect the interior of the appliance from precipitation.

In addition, of course, stack means that have been provided to overcome the above mentioned deficiencies, have their own considerable shortcomings which make their utilization undesirable. One objection is that the stack means heretofore provided are quite unsightly. Stacks are usually required by law or customs to extend over the surrounding structure such as fences or eaves. If the appliance is used as a swimming pool heater the unslightly stack usually is clearly visible and thus reduces the esthetic appearance of the surrounding a'rea. Additionally, one has to recognize the increased expense involved in the heretofore provided solutions to the mentioned problems.

The art also indicates that one could provide a plurality of baffles both interior and exterior the appliance to direct the primary and secondary air and the flue products properly so as to minimize the static pressure differential between the air intake and the outlet, that is the exhaust port.

In addition to being generally costly, fluid heaters heretofore necessarily equipped with draft diverters, barometric dampers, vent covers, spoilers, baffles or similar devices required for normal operation as an outdoor installation, were unsightly, generally inconvenient to install, and, most often required a variation of the designs for various different capacity appliances. Further, the appliances were designed either for outdoor or indoor installation, with conversion requiring substantial modifications.

Accordingly, it would be desirable to provide a fluid heater appliance which is capable not only of outdoor installation but also easily convertible to an indoor use without substantial modification of the design.

It is also desirable, in an effort to reduce the cost of the fluid heater appliance, to provide a structure which is capable of being assembled, disassembled and reassembled conveniently, thus reducing the cost of manufacture and also, preventing dislocation of the various operational sections of the appliance. In addition, it is desirable that all the advantages above mentioned be obtained without loss in the efficiency of the appliance and in fact perhaps with a gain in efficiency.

SUMMARY OF THE INVENTION There is provided a fluid heater which includes a housing, means defining air-intake means for introducing atmospheric air into the housing, means defining a combustion chamber interior of the housing, fuel burner means within said combustion chamber, control chamber means communicating between said airintake means and said combustion chamber, flue collector means disposed to receive the flue products of combustion from the combustion chamber, heat transfer means interposed between said flue collector means and said combustion chamber and capable of transferring generated heat energy from said flue products to a fluid carried therein, means defining an outlet duct communicating with said flue collector means, said outlet duct having port means for discharging said flue products from said outlet duct to the exterior of said housing and means for aspirating atmospheric air from said air-intake means to the control chamber means in controlled quantities, said aspirating means, including means capable of directing quantities of air in excess of said controlled quantity from said air-intake means to the exterior of said housing by-passing said control chamber.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. is a perspective view of the radiation shield illustrated in FIG. 4;

FIG. 6 is a perspective detail illustrating one of the support channels as shown in FIG. 2;

FIG. 7 is a fragmentary sectional view taken along lines 7-7 of FIG. 6 as viewed in the direction of the arrows;

FIG. 8 is a perspective detail illustrating one of the angle brackets illustrated in FIG. 2;

FIG. 9 is a fragmentary perspective view of a modified embodiment of the invention;

FIG. 10 is a fragmentary sectional view taken along lines 10-10 of FIG. 9 as viewed in the direction of the arrows;

FIG. 11 is a fragmentary sectional view taken along lines 11-11 of FIG. 9;

FIG. 12 is a detail view in section of the front portion of the device illustrated in FIG. 11; and

FIG. 13 is a fragmentary detail of a channel member forming the side wall of the outlet chamber included in the device illustrated in FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, FIG. 1 illustrates a fluid heater appliance, indicated generally by reference character 10, that is adapted to be used as an outdoor water heater for swimming pool water. Appliance 10 illustrated herein is a gas burning device, although other fuels can be utilized and as well, other fluids can be heated.

The fluid heater appliance 10 comprises an exterior housing 12 defined by front and rear walls 14 and 14', a pair of opposite side walls 16, a base 18 and an exterior cover 20. The base 18 is formed as a generally U- shaped channel member having depending feet 22 along the edges thereof. The walls are secured to the base 18 along the edges of said base, each wall having flange means 24 for securement to the feet 22 of said base 18 whereby to enclose the interior of the appliance 10. The front wall 14 is removable to permit access to the interior of the appliance.

A combustion chamber 26 is defined by fire walls 28 which are supported on channels 30, 30 and 30", channels 30 and 30' being secured to the base 18, thereby defining a rectangular enclosure forming the combustion chamber. The channels 30 each include horizontal flange 32 having upstanding tabs 34 formed therein, as by cutting U-shaped slits through the flange 32 and bending the cutout portions to an upright disposition relative to flange 32. Flange 32 has an offset depressed edge portion 32. L-shaped flange 36 is secured, as by spot welding along the free edge thereof to the flange 32 so that a slot 36' is defined between it and flange portion 32'. This provides means for sliding radiation shield 84 in and out after assembly of the remainder of apparatus 10. Each fire wall 28 which defines the combustion chamber 26 is seated on flange 32 between tabs 34 and flange 36. The fire walls 28 are formed of a castible refractory material.

Heat transfer means in the form of a conventional heat exchanger 38 is located directly above the combustion chamber 26 adjacent to the upper ends 40 of the fire walls 28. The heat exchanger 38 comprises a bank of conduits 42 providing a continuous path for the fluid to be heated. The ends of said conduits 42 are secured to header means 44, including inlet and outlet ports 46 and 48 respectively. Generally the conduits are thin-walled finned tubes 50 and may include baffle means 52 to distribute the so-called flue products over the extent of the heat exchanger 38. The fluid to be heated is introduced into the tubes 50 with suitable temperature measuring means (not shown) provided to regulate the operation of the appliance in accordance with the needs for heating the fluid.

A flue collector 54 of generally rectangular cross section substantially is provided including a portion generally similar to the cross section of combustion chamber 26. The flue collector 54 is positioned with its bottom edges 56 mounted to the heat exchanger 38 and to the upper ends 40 of the fire walls 28. A pair of angle brackets 58, each having a plurality of extensions or tabs 60 cooperating with the upper ends 16' of the exterior walls 14, 14' and 16 act to interlock the position of the flue collector 54 relative to the remaining structure. A pair of duct walls 62 and 64 each having an angle shaped cross section, further restrain the pair of brackets 58 from dislocating, thus completely restraining the movement of the flue collector 54 and preventing its dislocation.

The exterior cover is mountable directly to the upper ends 66 of the exterior walls 14, 14' and 16. A plurality of gas burners 68 are positioned longitudinally spaced across the mouth 70 of the combustion chamber 26 with each burner 68 extending completely across the mouth 70. One end 72 of each gas burner 68 is coupled to conventionally constructed gas supply means (not shown). The opposite end 74 of each burner 68 is sealed and mounted to the rear wall 85 of the radiation shield 84 by passing through L-shaped slots 87. The end 72 is open to permit entrainment of air by the gas received from said gas supply means, this entrained air called primary air.

A vertically arranged interior wall 76 bridges the front of the housing 12 spaced rearwardly of front wall 14 and is secured, on two sides, to the side walls 16. Wall 76 cooperates with front wall 14 and those portions of the side walls 16 to define a control chamber 78 which houses the gas supply means, valves and other control means (not shown), including the header means 44 containing the temperature control means (not shown). Wall 76 prevents the header means from becoming a part of the chamber 78. The control compartment 78 also defines the first of a pair of air feed chambers to be discussed hereinafter.

The interior wall 76, at its lower end, is integral with the channel which supports the front fire wall 28. A bottom radiation shield 84 is provided with two spaced side walls 80, 82 which join with support channels 30, 30' and cooperate with the base 18 to form a pair of passageways 86 extending parallel to the side walls 16. The radiation shield 84 is shown in perspective in FIG. 5 with the passageways 86 being visible in FIG. 4.

An aperture 88 is defined at the rear portion of the walls 80, 82 of radiation shield 84 so as to permit communication of the passageways 86 with the interior of the combustion chamber 26. Each aperture 88 has adjacent thereto and extending into the passageway, a guide panel 90 which aids in the turbulent free transfer of air from said passageways 86 to the combustion chamber 26.

A plurality of somewhat regularly spaced perforations 92 are formed in parallel rows near the upper ends 16 portion of the exterior side walls 16 to permit communication between atmosphere and a pair of passageways 94, 96 defined by the pair of angle brackets 58, the flue collector 54, and the heat exchanger means 26 in cooperation with the exterior walls l4, 16. The pair of passageways 94, 96 also are in communication one with the other by way of front and rear passageways 98, 100. Passageway 98 is defined across the front of the appliance 10 by the flue collector 54 and the upper portion of the adjacent fire walls 28, in cooperation with the front wall 14. The rear disposed passageway 100 is defined between the rear wall of flue collector 54 and the rear wall 14' in cooperation with one of the fire Walls 28. The passageway 98, which shall be defined in terms of its principal function, that is of an air intake chamber, is in communication with the interior of the combustion chamber 26 by way of restricted airflow means in the form of aperture 102 formed in bridging wall 104 connecting the front wall 14 with the interior wall 76 and leading to control chamber 78. The fire walls 28 are spaced a small distance from the adjacent exterior walls to define a somewhat stagnant-air space 105 serving to heat insulate the appliance 10. The dead air space 105 also provides an escape path for precipitation entering the appliance.

A plurality of perforations 106, 106 are formed on the forward and rearward regions of the exterior cover panel 20 so as to permit communication with outlet chamber or duct 108 which is defined by cooperation of the pair of angle brackets 58, duct walls 110 and 112, the flue collector 54 and the exterior cover panel 20. The flue collector 54 is provided with an aperture 114 so as to permit communication between the outlet chamber or duct 108 and the combustion chamber by way of the spaces between the tubes or conduits 42 of the heat exchanger 38 and said flue collector 54.

The exterior cover panel 20 is provided with a centrally located aperture or outlet 116 which can be closed with a removably secured cover plate 118. Any precipitation, such as rain, entering the outlet duct 108 by way of the perforations 106, 106 formed in the exterior cover panel 20 will be discharged from the outlet duct 108 through a plurality of drain holes (not shown) provided in the floor 109 thereof into the dead-air spaces 104. Any rain entering the spaces 104 from the outlet duct 108 or entering through the perforations 35 in the side walls 16, will drop to the base 18 and be discharged from the appliance 10 through a plurality of drain holes located thereon (not shown).

In operation, gas under pressure is supplied to the gas burners 68, there mixed with primary air received through aperture 102 by way of control chamber 78 and is ignited initially by a conventional pilot burner (not shown) as the'primary air-gas mixture leaves the burner interior through a plurality of burner ports 69 of the burners 68. The primary air-gas mixture then combusts within the combustion chamber 26 aided by a quantity of secondary air which is required to complete the combustion process. The so-called secondary air is, defined as air traveling by way of aperture 102 and control chamber 78 other than the air entrained into the burners 68 by the gas. The flue products of combustion which are created within the confines of the combustion chamber 26 are transferred upwards by convection through the spaces between the conduits 42 of the heat exchanger 38 where the major portion of the heat energy of such flue products of combustion is transferred to the fluid moving through the conduits 42 of the heat exchanger 38. Thus, the temperature of the air intake chamber 98, thence is aspirated through aperture 102 into the control compartment 78 and transferred by way of natural draft to the interior of radia-.

tion shield 84 and passageways 86 defined by walls 80, 82 of radiation shield 84, thence to the burners 68 and combustion chamber 26. The amount of air admitted into the control chamber 78 is determined by the cross section of aperture 102. The required amount of primary air enters the burhers for mixing with the gas fuelv The required quantity of secondary air is transferred to the combustion chamber by way of passageways defined between the walls 80 and 82 of radiation shield 84 and the support channels 30, and also, by moving through the pair of passageways 86 defined between the walls of the housing and the exterior of the radiation shields. Each of walls 80 and 82 of radiation shield 84 is provided with a pair of angularly outwardly extending baffles or guide panels 90 defining a pair of apertures 88. The manner of supplying secondary air to the combustion chamber results in the uniform supply with reduced turbulence to the plurality of burner ports 69 thus increasing flame stability and improving the combustion process. The guide panels 90 function to reduce turbulence.

Under excessive wind conditions, the quantity of primary and secondary air required for complete combustion and a quantity of additional or excess air enters through the air-intake means defined by the plurality of perforations 92 into the air-intake chamber 98. The desired quantity of primary and secondary air is transferred to the control chamber 78 by means of aperture 102 and directed to the combustion chamber as described above. The additional or excess quantity of air which is not required for completing the combustion, is transferred directly from the air intake chamber 98 to passageway 100 by way of the side passageways 94 and 96 and from there, is discharged through perforations 92 in wall 14 to the exterior of appliance 10. If the gusts of air enter the appliance by way of perforations 92 in wall 16, the air will travel by way of passageway 100 to side passageways 94, 96, then to passageway 98 where the required quantity will pass through aperture 102, the excess or remainder exiting by way of perforations 92 of wall 16. It should be noted that perforations 92 are of rectangular configuration but, of course may take other shapes.

It should be noted that the gas burning heater appliance 10 impedes the excessive wind or gust causing an increased pressure at the plurality of perforations facing the direction of the path of the wind or gusts, and also causes a decrease in pressure at the plurality of perforations 92 on the opposite side of the gas fired appliance 10. A similar pressure differential will be created by the same wind or gust at the plurality of perforations 106, 106 formed in the exterior cover. Accordingly, any air which is caused to enter the plurality of perforations 106 in one region of the exterior cover, which faces the direction of the path of wind or gust, is discharged together with the flue products of combustion to the exterior of the housing 12 by way of the plurality of perforations 106 formed in the other region of the cover panel 20.

It should be further noted that any wind or gusts acting on a path downward will be impeded by the exterior cover panel and cover plate thus preventing air from entering the combustion chamber through the aspirating aperture 102 leading to the control chamber 78.

It should be further noted that because the inner walls of air intake chamber 98 and of the passageways 94, 96 and are formed by the flue collector. the primary and secondary air required for complete combustion is brought into intimate contact with the flue collector walls and thus heat energy is transferred by conduction through said walls from the flue products by way of the flue collector walls to the primary and secondary air. In this way, the temperature of the flue products is reduced and the temperature of the primary and secondary air is increased. Accordingly, by this means, the stack losses will be reduced and the efficiency of the combustion process and flame stability will be improved.

It should be noted that no stack means whatsoever are required to be connected to the outlet port 116 of the outlet duct 108 and further, no barometric dampers, vent covers, spoilers, baffles or the like are required. Valve means shown in broken outline, may be provided at the aspirating aperture 102 so as to control, i.e., to vary, the input rating to enable the appliance to be modified to operate on a much smaller quantity of gas supply simply by varying the size of the aspirating aperture 102.

The appliance 10 can be installed indoors simply by removing the cover plate and inserting a conventional draft diverter (not shown) through the outlet 116 and duct 108, mounting said draft diverter t0 the discharge port 114 of the flue collector already formed of standardized size and configuration capable of receiving such draft diverter. The draft diverter then is connected to the conventional outside air ducting in a conventional manner. Outlets 114 and 116 preferably are axially aligned to enable a tubular stack (not shown) to be introduced therein if desired.

Referring now to FIG. 9, a portion of a modified embodiment of the invention is illustrated, the modified fluid heater appliance being designated generally by reference character 10'. Fluid heater 10 is substantially identical to fluid heater appliance 10 but for the outlet chamber 120 thereof. The outlet chamber 120 of appliance 10 is defined by a pair of side walls 122 and 124 and a pair of perforate walls 126 and 128 arranged to define the front and rear respectively of said outlet chamber 120. The walls 122, 124, 126 and 128 are formed of U-shaped channeled members. The bottom wall 130 is seated upon the flue collector in the same manner as shown in the description of appliance 10. A port 132 is formed in the bottom wall 130 of the outlet chamber 120 in communication with the interior of the flue collector.

The top wall of the outlet chamber 120 is defined by cover panel 134. Cover panel 134 carries a port 136 axially aligned with port 132. Removable cover 138 is provided to close off port 136. Except for port 136, exterior cover 134 is imperforate, the perimetric edges thereof being secured to said walls 122, 124, 126 and 128.

Both the front and rear walls 126 and 128 are provided with spaced openings 140 so as to define a through path in the outlet chamber in a straight line from the front to the rear of the appliance The channel members defining the outlet chamber walls, that is the side walls 122, 124 and front and rear walls 126, 128, comprise U-shaped sections 141 having top 1 and bottom flanges 144 and 146, with the bottom flanges 146 only of walls 122 and 124 having depending tabs 148 formed by slitting said flange 146 in spaced locations along its length and bending the resulting slit portions at an angle relative to the flange 146. The tabs 148 so defined interlock with edge flange 129 of floor 130 of the outlet chamber with the remaining flange 146 fixedly secured to flanges 152 provided at the upper ends of the exterior walls of the housing 12'.

What we claim is: e

1. A fluid heater comprising a housing, means defining air-intake means for introducing atmospheric air into the cabinet, means defining a combustion chamber interior of the housing, fuel burner means within said combustion chamber, control chamber means communicating between said air-intake means and said combustion chamber means for feeding air thereinto, flue collector means disposed within said housing to receive the flue products of combustion from the combustion chamber means, heat transfer means interposed between the flue collector means and the combustion chamber means in intercepting relation to the path of said flue products and capable of transferring generated heat energy from said flue products to a fluid carried within said heat transfer means, means defining an outlet duct communicating with said flue collector means, said outlet duct including port means for discharging said flue products from said outlet duct to the exterior of the housing and means for aspirating atmospheric air from said air-intake means to the control chamber means in controlled quantities and including means capable of directing quantities of air in excess of said controlled quantity from said air-intake means to the exterior of said housing by-passing said control chamber.

2. The fluid heater as claimed in claim 1 wherein said housing includes front, rear and side walls, said airintake means comprising plural perforations formed at least in said side walls near the upper portions thereof between said front and rear walls, and said aspirating means comprises at least one passageway formed interior of said housing, said plural perforations opening into said passageway and means defining a restricted orifice interposed between said passageway and said control chamber and said passageway also opening to the exterior of said housing at a location spaced from said control chamber.

3. The fluid heater as claimed in claim 2 in which said means defining a restricted orifice comprises a wall separating said passageway from said control chamber and an aperture defining the sole entry to said control chamber through said wall.

4. The fluid heater as claimed in claim 3 in which said means defining a restricted orifice includes valve means for varying the diameter of said aperture.

5. The fluid heater as claimed in claim 2 in which said housing and said flue collector is in heat exchange relation with said passageway.

6. The fluid heater as claimed in claim 1 in which said housing includes a cover defining the top wall thereof.

7. The fluid heater as claimed in claim 6 in which said cover forms one wall of said outlet duct and port means formed in said cover for discharging said flue products from said duct.

8. The fluid heater as claimed in claim 6 in which said port means includes an outlet spaced from the edges of said cover and second cover means removably secured to said cover.

9. The fluid heater as claimed in claim 1 in which said combustion chamber is spaced from the walls of said housing to substantially define surrounding dead-air spaces.

10. The fluid heater as claimed in claim 1 in which said housing includes an upper covering wall and said covering wall has perforations formed therein, said covering wall forming one wall of said outlet duct.

11. The fluid heater as claimed in claim 7 in which said port means includes at least two groups of perforations formed in said cover and arranged spaced apart one group from the other.

12. The fluid heater as claimed in claim 10 in which said perforations are arranged in at least two groups, one group spaced from the other.

13. The fluid heater as claimed in claim 12 in which there is a removably covered port disposed between said groups.

14. The fluid heater as claimed in claim 2 in which said plural perforations are arranged in at least one row along the side and rear walls.

15. The fluid heater as claimed in claim 2 in which said outlet duct is disposed over said flue collector means and extending across substantially the entire upper portion of the housing, said housing including a top wall defining, with said side walls, front and rear walls, said outlet duct.

16. The fluid heater as claimed in claim 15 in which said passageway is defined between the housing and the flue collector and extends along the side and rear wall of said housing, said perforations opening to said passageway.

17. The fluid heater as claimed in claim 1 in which said port means comprise plural perforations formed in the end walls of the duct at the front and rear walls of the housing.

18. The fluid heater as claimed in claim 17 in which said end walls are recessed.

19. The fluid heater as claimed in claim 16 in which said top wall is spaced from the upper ends of said front, rear and side walls of said housing, imperforate spacing wall means secured to the top wall and to the upper ends of said front, rear and side walls to define a recess, and said port means comprise perforations formed in said spacing wall means whereby to define a clear channel opening to the front and rear of the housmg.

20. The fluid heater as claimed in claim 19 in which there is an interior horizontal wall seated upon said flue collector means and forming the bottom wall of said outlet duct, said horizontal wall having a port formed therein arranged to communicate with said flue collector means.

21. The fluid heater as claimed in claim in which said interior horizontal wall is spaced from said spacing wall means to define a path communicating to at least one said passageway.

22. A fluid heating device comprising a housing, a combustion chamber within the housing, burner means for combusting fuel within said combustion chamber, heat transfer means capable of carrying fluid and disposed in communication with said combustion chamber to intercept the combustion products for transferring the generated heat energy from said combustion products to the fluid, wall means defining at least two inlet chambers within said housing, air-intake means formed in said housing in communication with said inlet chambers, means defining a passageway between said inlet chambers and communicating to said combustion chamber and burner means, flue collector means for receiving said combustion products subsequent to passage thereof past said heat transfer means, means defining at least one outlet chamber in communication with said flue collector, first port means formed in said flue collector to enable passage of combustion products thereinto and second port means formed in said outlet chamber for discharge of said combustion products to the exterior of said housing and air-flow restriction means disposed within said passageway whereby a given quantity of air from said airintake means is introduced into said combustion chamber and burner means and air quantities in excess of said given quantity are directed through said housing by way of said inlet chambers to and through said airintake means to the exterior of the housing.

23. The fluid heating device as claimed in claim 22 in which at least one wall of each inlet chamber is defined by said flue collector and another wall thereof is defined by said housing, said last mentioned wall having a plurality of perforations formed therein and comprising said air-intake means.

24. The fluid heating device as claimed in claim 22 wherein at least one wall of each inlet chamber is in heat-exchange relationship with said flue collector.

25. The fluid heating device as claimed in claim 22 in which said wall means defining said inlet chambers and said passageway include said flue collector, and said air-intake means comprises a plurality of perfora- 12 tions substantially co-extensive with said inlet chambers.

26. The fluid heating device as claimed in claim 22 and means interior of said housing defining a feeding chamber forming a flow path leading to said combustion chamber from-said air-flow restriction means.

27. The fluid heating device as claimed in claim 26 in which said air-flow restrictor means comprise valve means.

28. The fluid heating device as claimed in claim 26 in which said feeding chamber includes radiation shield means interposed in the air-flow path adjacent the entrance to said combustion chamber, said radiation shield means including leg means defining a first path adjacent said housing and leading to said combustion chamber and a second path between said leg means, said burner means being arranged in said second path whereby primary air is introduced therein for mixing with said fuel and secondary air is introduced to said combustion chamber by way of said first and second paths.

29. The fluid heating device as claimed in claim 28 in which baffle means is formed in said leg means in intercepting relation relative to said first path.

30. The fluid heater as claimed in claim 22 in which said second port means comprises openings formed in a pair of oppositely disposed walls of said outlet chamber to define a path in a direction substantially normal to the axis of said first port means and the flow of combustion products into said outlet chamber.

31. The fluid heater as claimed in claim 22 in which said second port means comprises at least one opening formed in the wall of said outlet chamber opposite to the first port means.

32. The fluid heater as claimed in claim 31 in which said first and second port means are axially aligned to enable introduction of an exterior tubular stack member therethrough.

33. The fluid heater as claimed in claim 22 in which said second port means includes plural openings formed in said wall of said outlet chamber.

34. The fluid heater as claimed in claim 33 in which said plural openings are disposed in at least two groups spaced one from the other. 

1. A fluid heater comprising a housing, means defining airintake means for introducing atmospheric air into the cabinet, means defining a combustion chamber interior of the housing, fuel burner means within said combustion chamber, control chamber means communicating between said air-intake means and said combustion chamber means for feeding air thereinto, flue collector means disposed within said housing to receive the flue products of combustion from the combustion chamber means, heat transfer means interposed between the flue collector means and the combustion chamber means in intercepting relation to the path of said flue products and capable of transferring generated heat energy from said flue products to a fluid carried within said heat transfer means, means defining an outlet duct communicating with said flue collector means, said outlet duct including port means for discharging said flue products from said outlet duct to the exterior of the housing and means for aspirating atmospheric air from said air-intake means to the control chamber means in controlled quantities and including means capable of directing quantities of air in excess of said controlled quantity from said air-intake means to the exterior of said housing by-passing said control chamber.
 2. The fluid heater as claimed in claim 1 wherein said housing includes front, rear and side walls, said air-intake means comprising plural perforations formed at least in said side walls near the upper portions thereof between said front and rear walls, and said aspirating means comprises at least one passageway formed interior of said housing, said plural perforations opening into said passageway and means deFining a restricted orifice interposed between said passageway and said control chamber and said passageway also opening to the exterior of said housing at a location spaced from said control chamber.
 3. The fluid heater as claimed in claim 2 in which said means defining a restricted orifice comprises a wall separating said passageway from said control chamber and an aperture defining the sole entry to said control chamber through said wall.
 4. The fluid heater as claimed in claim 3 in which said means defining a restricted orifice includes valve means for varying the diameter of said aperture.
 5. The fluid heater as claimed in claim 2 in which said housing and said flue collector is in heat exchange relation with said passageway.
 6. The fluid heater as claimed in claim 1 in which said housing includes a cover defining the top wall thereof.
 7. The fluid heater as claimed in claim 6 in which said cover forms one wall of said outlet duct and port means formed in said cover for discharging said flue products from said duct.
 8. The fluid heater as claimed in claim 6 in which said port means includes an outlet spaced from the edges of said cover and second cover means removably secured to said cover.
 9. The fluid heater as claimed in claim 1 in which said combustion chamber is spaced from the walls of said housing to substantially define surrounding dead-air spaces.
 10. The fluid heater as claimed in claim 1 in which said housing includes an upper covering wall and said covering wall has perforations formed therein, said covering wall forming one wall of said outlet duct.
 11. The fluid heater as claimed in claim 7 in which said port means includes at least two groups of perforations formed in said cover and arranged spaced apart one group from the other.
 12. The fluid heater as claimed in claim 10 in which said perforations are arranged in at least two groups, one group spaced from the other.
 13. The fluid heater as claimed in claim 12 in which there is a removably covered port disposed between said groups.
 14. The fluid heater as claimed in claim 2 in which said plural perforations are arranged in at least one row along the side and rear walls.
 15. The fluid heater as claimed in claim 2 in which said outlet duct is disposed over said flue collector means and extending across substantially the entire upper portion of the housing, said housing including a top wall defining, with said side walls, front and rear walls, said outlet duct.
 16. The fluid heater as claimed in claim 15 in which said passageway is defined between the housing and the flue collector and extends along the side and rear wall of said housing, said perforations opening to said passageway.
 17. The fluid heater as claimed in claim 1 in which said port means comprise plural perforations formed in the end walls of the duct at the front and rear walls of the housing.
 18. The fluid heater as claimed in claim 17 in which said end walls are recessed.
 19. The fluid heater as claimed in claim 16 in which said top wall is spaced from the upper ends of said front, rear and side walls of said housing, imperforate spacing wall means secured to the top wall and to the upper ends of said front, rear and side walls to define a recess, and said port means comprise perforations formed in said spacing wall means whereby to define a clear channel opening to the front and rear of the housing.
 20. The fluid heater as claimed in claim 19 in which there is an interior horizontal wall seated upon said flue collector means and forming the bottom wall of said outlet duct, said horizontal wall having a port formed therein arranged to communicate with said flue collector means.
 21. The fluid heater as claimed in claim 20 in which said interior horizontal wall is spaced from said spacing wall means to define a path communicating to at least one said passageway.
 22. A fluid heating device comprising a housing, a combustion chamber within the housing, burner means for comBusting fuel within said combustion chamber, heat transfer means capable of carrying fluid and disposed in communication with said combustion chamber to intercept the combustion products for transferring the generated heat energy from said combustion products to the fluid, wall means defining at least two inlet chambers within said housing, air-intake means formed in said housing in communication with said inlet chambers, means defining a passageway between said inlet chambers and communicating to said combustion chamber and burner means, flue collector means for receiving said combustion products subsequent to passage thereof past said heat transfer means, means defining at least one outlet chamber in communication with said flue collector, first port means formed in said flue collector to enable passage of combustion products thereinto and second port means formed in said outlet chamber for discharge of said combustion products to the exterior of said housing and air-flow restriction means disposed within said passageway whereby a given quantity of air from said air-intake means is introduced into said combustion chamber and burner means and air quantities in excess of said given quantity are directed through said housing by way of said inlet chambers to and through said air-intake means to the exterior of the housing.
 23. The fluid heating device as claimed in claim 22 in which at least one wall of each inlet chamber is defined by said flue collector and another wall thereof is defined by said housing, said last mentioned wall having a plurality of perforations formed therein and comprising said air-intake means.
 24. The fluid heating device as claimed in claim 22 wherein at least one wall of each inlet chamber is in heat-exchange relationship with said flue collector.
 25. The fluid heating device as claimed in claim 22 in which said wall means defining said inlet chambers and said passageway include said flue collector, and said air-intake means comprises a plurality of perforations substantially co-extensive with said inlet chambers.
 26. The fluid heating device as claimed in claim 22 and means interior of said housing defining a feeding chamber forming a flow path leading to said combustion chamber from said air-flow restriction means.
 27. The fluid heating device as claimed in claim 26 in which said air-flow restrictor means comprise valve means.
 28. The fluid heating device as claimed in claim 26 in which said feeding chamber includes radiation shield means interposed in the air-flow path adjacent the entrance to said combustion chamber, said radiation shield means including leg means defining a first path adjacent said housing and leading to said combustion chamber and a second path between said leg means, said burner means being arranged in said second path whereby primary air is introduced therein for mixing with said fuel and secondary air is introduced to said combustion chamber by way of said first and second paths.
 29. The fluid heating device as claimed in claim 28 in which baffle means is formed in said leg means in intercepting relation relative to said first path.
 30. The fluid heater as claimed in claim 22 in which said second port means comprises openings formed in a pair of oppositely disposed walls of said outlet chamber to define a path in a direction substantially normal to the axis of said first port means and the flow of combustion products into said outlet chamber.
 31. The fluid heater as claimed in claim 22 in which said second port means comprises at least one opening formed in the wall of said outlet chamber opposite to the first port means.
 32. The fluid heater as claimed in claim 31 in which said first and second port means are axially aligned to enable introduction of an exterior tubular stack member therethrough.
 33. The fluid heater as claimed in claim 22 in which said second port means includes plural openings formed in said wall of said outlet chamber.
 34. The fluid heater as claimed in claim 33 in which said plural openings are disposed in at least two groups spaced one from the other. 